Automatic tracer assembly for copying machine tools

ABSTRACT

The tracer assembly for copying machine tools comprises a tracer mounted intermediate its length in a housing by means of a diaphragm so as to be capable of oscillating in all directions and moving in axial direction, for tracing the pattern and controlling the feed movement of the machine tool. This tracer assembly comprises an automatic precontrol unit to impart to the tracer a contact pressure towards the pattern according to the direction of the contacting tangent between the pattern and the tracer tip and situated in the copying line plane. A feeling member is provided which is responsive to tracer deflections occurring outside of the copying line plane, and which is coupled with a correcting element acting against the precontrol unit.

United States Patent Inventor Otto Ronner Rorclmcherberg/SG, SwitzerlandAppl. No. 778,946 Filed Nov. 26, 1968 Patented Jan. 4, 1972 AssigneeStarrfrasmachinen A.G.

St. Gallen, Switzerland Priority Nov. 27, 1967 Switzerland 16620/67AUTOMATIC TRACER ASSEMBLY FOR COPYING MACHINE TOOLS [56] ReferencesCited UNITED STATES PATENTS 3,l14,295 12/1963 Ronner etal. 90/62 PrimaryExaminerGil Weidenfeld AttorneyFitch, Even, Tabin & Luedeka ABSTRACT:The tracer assembly for copying machine tools comprises a tracer mountedintermediate its length in a housing by means of a diaphragm so as to becapable of oscillating in all directions and moving in axial direction,for tracing the pattern and controlling the feed movement of the machinetool. This tracer assembly comprises an automatic precontrol unit toimpart to the tracer a contact pressure towards the pattern according tothe direction of the contacting tangent between the pattern and thetracer tip and situated in the copying line plane. A feeling member isprovided which is responsive to tracer deflections occurring outside ofthe copying line plane, and which is coupled with a correcting elementacting against the precontrol unit.

PATENTEU JAN 4 i372 SHEET 1 [IF 5 ll 11 Ill INVENTOR. OTTO EON N E 2PATENTEDJAN 41972 3631759 sum 2 or s INVENTOR. OTTO EON N E2 PATENTEBJAN 4x912 3631.759

sum 3 BF 5 0.04 omgmm 0 Fig.18 11,119 F1920 Fig. 21 Fig. 22

F /'g. 72 Fig. 13 Fig. 74 Fig. 75 F1916 Fig. 17

Advance Direchon Advance Dmeclzion INVENTOR. OTTO RON NE 2 PATENTEDJAN41972 SHEET '4 BF 5 Fig. 24

INVENTOR. OT TO RON NE E.

PATENTEDJAN M972 363L759 sum 5 or 5 INVENTOR. OTTO EON NEE AUTOMATICTRACER ASSEMBLY FOR COPYING MACHINE TOOLS The present invention relatesto an automatic tracer assembly for a copying machine tool and having atracer member arranged to be axially movable and mounted to effect apivoting or wobbling motion, intended for tracing a pattern and forcontrolling the feed movement of the machine tool, and having anautomatic precontrol unit acting on the tracer, in order to impart tosaid member, in dependence upon the direction of the contacting tangentbetween the pattern and the end of the tracer in the plane of thecopying line, a precontrolling force lying in this plane and acting onthe pattern.

Such as feeler or tracer is, for example, described in detail in US.Pat. No. 3,114,295.

In the majority of the known line copying systems, a feeler or tracer isprovided which is deflectable in all directions from a central position.It is, therefore, possible also to copy surface sections on the patternwhich are practically parallel to the copying line plane (calledhereinafter sidewalls). The feeler or tracer deflection characteristicis thus elliptic, that is to say, when encountering an obstacle, greaterdeflections, e.g., 0.25 mm. and more, occur in the copying line planerectangularly thereto (in the line step direction). In order tocompensate for this characteristic which influences the accuracy of sizeof the machined workpiece, a feeler or tracer could basically be usedwhose section remains elliptic and whose end is formed as an ellipsoid.Since, however, a feeler or tracer of this type can hardly be producedeconomically, a round feeler or tracer is mostly used in practice andthe sidewalls are machined after a first machining travel in a secondtravel with line direction turned through 90.

In a further known copying system with forward motion of the tracer, thelatter may, in the case of three-dimensional copying, only be deflectedin the advance direction, i.e. in the copying line plane, but is lockedin the line step direction. If and when such a tracer encounters asidewall of the pattern which forms with the copying line plane an acuteangle of only a few degrees, the tracer, before it is deflected in thecopying line plane, is deformed in a plane, transverse thereto, with theresult that too much material is removed from the workpiece which is,therefore, undersize. The danger of a deformation of the tracer in thecase of these sliding supports" which occurs relatively often betweensidewall and copying line plane is thereby logically greater as thetracer is selected to be thinner. In this way, from a predetermineddegree of wedging" onwards, the result may be that the advance motion ofof the tracer is mainly prevented.

It is an object of the present invention to provide an automatic tracerassembly of the type mentioned above wherein these disadvantages areminimized or substantially overcome.

In a tracer assembly according to the invention, a tracer member isprovided, that responds to tracing deflections resulting outside thecopying line plane, said member being coupled to a correcting elementwhich acts against the precontrol unit.

Thus, in a tracer assembly according to the invention, all tracerdeflections which have a component lying outside the copying line plane,are picked up by the said member and transferred to the correctionelement which, due to its effect directed against the precontrol unit,simulates to a certain extent the effect of a limiting shape which wouldonly produce a tracing deflection lying in the copying line plane. Theprecontrol unit then reacts corresponding to this simulated limitingshape and changes the direction of the precontrolling force on thetracer until said feeler, apart from a response threshold, no longer hasany deflection outside the copying line plane.

The proposed device consequently makes it possible to machine in onepass, dies and other three-dimensional shapes independently of theirshape in the advance region usual for such shapes with a tracer diameterenlargement by 0.1 to 0.2 mm. independently of the advance motion, saiddies being ready for use and true to size.

Some preferred embodiments of the invention will now be hereinafter moreclearly explained, with reference to the accompanying drawings, inwhich:

FIG. 1 shows a first embodiment in schematic section in a plane verticalto the copying line plane,

FIG. 2 shows a section along the line 2--2 of FIG. 1 at the level of thecentering stops for the tracer member,

FIGS. 3 to 5 show schematic views in the copying line plane with theomission of certain parts in order to explain the function,

FIGS. 6 to 10 show a second embodiment with a correcting element havingtwo correction members which may be switched on and off as desired,

FIGS. 11 to 22 show a third embodiment in which the correcting elementoperates indirectly on the precontrol unit, FIG. 11 being a wholerepresentation similar to FIG. 1 and FIGS. 12-22 being simplified viewsin order to explain the mode of operation of this embodiment,

FIGS. 23 to 25 show a further embodiment similar to FIG. 1 wherein,however, the correcting element is drawn near the tracer in order tomove the reference position of the transmitter controlling theprecontrol unit itself, and

FIGS. 26-28 show another embodiment wherein the correcting element takesthe form of two solenoids which act directly on the tracer members.

Referring now to the drawings, as may be seen in FIGS. 1 to 5, a tracermember or pin 5 is suspended in the center of a housing 1, from adiaphragm 6. Said pin 5 and consequently a tracing element 11 insertedthereon are mounted to efl'ect a pivoting or wobbling motion about apoint located approximately at the level of the diaphragm 6, and theseparts 5 and 11 are also axially movable. The pin 5 serves to transferthe scanned shapes of a pattern onto the workpiece machined by the tool.This transfer is effected by data converters which have only been shownschematically in FIG. 3 and are commonly designated by 31 and 33, andwhich in known manner control the copying movement in two coordinatesbetween tool and workpiece. A more detailed description of these dataconverters 31, 33 is unnecessary since the connection between the tracerand the pattern belongs on the one hand to the tool and workbench butper se form no part of the invention; this connection may be hydraulic,electrohydraulic or completely electrical.

From the upper end of the pin 5, there projects a cylindrical pin 12whose axis is at right angles both to the axis of the pin 5 and to thecopying line plane. The cylindrical pin 12 engages in the limiting bore29 of a precontrol unit 18 which may be rotated substantially coaxiallywith respect to the pin 12. There is pivotally mounted at on thisprecontrol unit a cranked lever 14, on one arm of which is rotatablymounted a roller 13 which presses against the pin 12 under the effect ofa compression spring 19 pressing on the other arm of the cranked lever14 via a coupling and which attempts to press said pin 12 into aneccentric position with respect to the limiting bore.

The coupling which has just been described has a core 21 of an inductivedata converter indicated at 22 which for its part operates, via anamplifier 17, a servomotor 16 which rotates the precontrol unit (partsl3, 14 18) via a pinion 15 as long as the data transmitter 22establishes a position of the roller 13 (and consequently of the pin 12in the limiting bore 29) deviating from a predetermined position. Themutual cooperation of the precontrol unit and tracer is explained ingreat detail in the above mentioned US. Pat. No. 3,114,295, so that hereno indication need be made thereto.

It is only adjusted so much that the position of the roller 13 andconsequently the direction of the precontrol force exerted on the pin 5is independent upon the tracer deflection in the copying line plane,i.e., in practice, upon the contacting tangent lying in this planebetween element 11 and the pattern.

The pin 5 is resiliently centered in the copying line plane. To thisend, two levers 25 each pivotably about an axis 24 are provided on thelower closure flange (not shown) of the housing 1, which levers areurged towards each other by a tension spring 23 onto a stop 28 which issecured to the closure flange. Adjusting screws 27 are screwed to thefree ends of the levers 25, and about half way along, the levers carryrollers 10, which lie on flattened sections of the pin 5. The adjustingscrews 27 are thereby set so that the pin in the copying line planemoves easily and without clearance between the levers 25, and can onlybe deflected out of this plane against the effect of the spring 23.

As FIG. 1 shows, the pin 5 is coupled to an inductive data converter 9in the form of an electromechanical transducer having a core 8 fastenedto the tracer member pin 5 to cover the movements of the pin outside thecopying line plane. The date converter 9 produces a signal dependentupon the position of its core 8 which signal is fed to an electromagnet4 via an amplifier and rectifier circuit 7 which has only been shownschematically here. This electromagnet 4 is of the type which produces aforce proportional to the feed voltage and remaining constant over theworking stroke. The armature of this magnet 4 acts on one end of a pin 2which is biassed by means of a spring 3 and which passes through anaxial bore (not shown) within the pin 12, and the other end of whichacts on an arm of a cranked lever 30 mounted to pivot at 30a on theprecontrol member 18. As indicated in FIG. 1, the swivel axis 30a of thecranked lever 30 is parallel to the swivel axis 14a of the cranked lever14 and the other arm of the cranked lever 30 lies diametrically oppositethe roller 13 with respect to the pin 12.

The mode of operation of the arrangement illustrated in FIGS. 1 to 5,may be outlined as follows. The copying movement in the copying lineplane occurs in the manner described in the above-mentioned U.S. patent.

If the pin 5 is pivoted, during the tracing of a line, by a sidewall 34(FIGS. 1,3) against the force of the spring 23 (FIG. 2) from the copyingline plane, the cranked lever 30 is actuated by the magnet 4 independence upon the signal produced by the data converter 9 which isproportional to the amount of lateral deflection of the pin 5. Thecranked lever 30 acts against the roller 13 via the cylindrical pin 12in the same manner as if the pin 5 would experience a deflection in thecopying line plane directly by the pattern, and thus slows down motionand causes the precontrol unit to rotate in a clockwise direction (FIG.4) whereby the direction of the precontrol force acting on the pin 5also changes. If the lateral displacement of the tracer member persists,the precontrol unit (and consequently the direction of the precontrolforce) is rotated further until the tracer pin (for removing the lateraldeflection) is raised out of the pattern threshold value. The sameprocedure occurs if the element 11 of the pin 5 is pivoted in oppositedirection from the copying line plane. As soon as the deflection of thepin 5 from the copying line plane decreases (whether due to too muchcorrection of the cranked lever 30 or due to a decreasing steepness ofthe sidewall), the process occurs in reverse direction, i.e., thetracer, having been increased again by the precontrol force, is pressedonto the pattern as indicated in FIG. 5.

FIGS. 6 to 10 illustrate an embodiment similar to that in FIGS. 1 to 5.Therefore, in order to simplify the representation, some of the figuresfor components common to both embodiments have been omitted. FIG. 6shows the upper part of the pin 5 suspended from the diaphragm 6 withits cylindrical pin 12 which engages in the limiting bore 29 of theprecontrol unit, and on which the roller 13 of this unit acts.

In this embodiment, the correcting element is divided into two correctormembers, each of which may be switched on and off by means of areversing switch 43 in dependence upon the direction of course of thelines. Each of these corrector members has its own cranked lever 48 or49.

The free arms of these cranked levers 48 and 49 are not arrangeddiametrically opposite the roller 13 with respect to the pin 12 but arerotated through an obtuse angle B, or B1 about [35 in the present case,so that the two ends of the cranked lever make a sector angle of about90 with respect to one another and with respect to the axis of the pin12. Each of the cranked levers 48 and 49 has its own actuating members,the cranked lever 48 having a thrust jacket 46, a cranked lever 42resiliently and pivotally mounted at 40 and a magnet 41 whose liftingforce is independent of the travel and is proportional to the feedvoltage, while the cranked lever 49 is provided with a push rod 47, acranked lever 51 resiliently and pivotally mounted at 50 and a magnet 45similar to the magnet 41.

According to the switched direction of travel of the lines (towards theright or left in FIGS. 7 to 10), either magnet 41 or 45 is preselectedby reversing switch 43 for activating the connecting members. In amovement towards the right, according to FIGS. 7 and 9, it is the magnet45 actuating the cranked lever 49. The position of this cranked levercorresponds in steady-state angular position of the precontrol roller13, to the position of the tangent on the traced pattern contour 32.This means that the cranked lever 49 may simulate a pattern contourlying in the copying line plane according to the actuation by the magnet45.

If the tracer is deflected by the sidewall 34 of right angles to theplane of the drawing of FIG. 7, the cranked lever 49 lifts the pin 5 onthe pin 12, thereby effects an upward advance movement as well as areduction of the horizontal advance components, but simultaneouslyeffects an outward pressure of the precontrol roller 13 which causes theprecontrol to rotate in clockwise direction (FIG. 8). Lying on thecranked lever, the pin 5 is precontrolled upwardly to an increasingextent by the rotating precontrol unit until that position of rotationis found (FIG. 8) in which the tracer is so deflected in the line planethat the advance motion is effected in the direction adapted to thesidewall. Each successive forward or return of the sidewall produces anincrease or decrease in the tracer side deflection and consequently achange in the amount of engagement of the cranked lever, and thereby acorrection of the position of rotation of the precontrol unit in theclockwise or anticlockwise direction until balance is again found (FIG.9).

Should the line direction be turned, a pivoting of about in ananticlockwise direction is given to the precontrol unit in order that itassumes the position according to FIG. 10, as described in U.S. Pat.specification, No. 3,114,295 mentioned above. Meanwhile, the transmitter9 is switched by the reversing switch 43 from magnet 45 to magnet 41 sothat now the cranked lever 48 takes over the work of the cranked lever49.

FIGS. 11 to 22 schematically show a further embodiment and its function.In this embodiment, the construction is basically the same as in theembodiment according to FIG. 6, so that the construction according toFIG. 11 will be referred to only shortly.

The electromagnets 61 and 65 are normal operating magnets which may beswitched on and off by the reversing switch 62 in dependence upon theadvance direction. The swivel axes 60 or 66 for the cranks 63 or 64 arefixed swivel pins in contrast to the resilient swivel pins 40 or 50(FIG. 6). The two cranks 48, 49 acting on the cylindrical pin 12 of thepin 5 are provided on their ends lying opposite the pin 12 withadjusting screws 67 which are so adjusted that when the cranked leversare operated, the pin 12 is pushed only to the exact center of thelimiting bore 29 (compare FIGS. 12, 13). The precontrol member 18 isprovided with a gear rim 68 rotating the whole precontrol unit with it,which is coupled via a gear wheel 69 of the same dimensions, to apotentiometer 72. The momentary adjustment of the potentiometer isconsequently characteristic for the momentary arrangement of theprecontrol unit and accordingly gives the potentiometer which isconnected to a reference voltage source (not shown) a signalcorresponding to the momentary position of the precontrol unit on thelead designated by 1st.

The servomotor 16 of the precontrol unit may, as shown in FIG. 11,either by actuated as in FIGS. 1 and 6, by an inductive data converter22 via amplifiers 17 or by the signal produced by a comparison switch 71which is also fed via the amplifier 17. The reversal from one to theother control is effected by a reversing switch relay 70. The comparisoncircuit 71 serves to compare the signal fed from the transmitter 9 viathe lead designated by 8011" with that of the potentiometer. Parallel tothe data converter 9 and coupled in the same manner to the pin 5 thereis provided a further data transmitter 74 which controls, via anamplifier 74a and a rectifier 74b, a threshold value switch 73 which forits part lies in the energizing circuit of the relay 70. In this way,the adjustment of the elements 73, 74, 74a and 74b is such that theswitch 73 closes as soon as the side deflection of the feeler tip on thepattern exceeds a predetermined value of, for example, 0.01 mm.

This embodiment is accordingly controlled so that the position ofrotation of the precontrol member 18, from a predetermined thresholdvalue of the side deflection, no longer regulates the precontrol roller13 but is regulated by the amount of side deflection.

FIGS. 12-22 schematically show the mode of operation of this embodiment.When the pattern contour 32 in the line plane is being copied (FIG. 12),the cranked levers 49 and 48 are out of engagement and have noinfluence. The rotation of the precontrol 18 is thereby regulated by thedata converter 22. However, as soon as the tracer is deflected on asidewall 34 in line step direction, relay 70 switches to precontrolproportional to side deflection, each side deflection of the tracerbetween 0.01 and 0.05 mm. being allocated a determined position ofrotation measured by the potentiometer 72 (FIGS. 13-22). At the sametime, according to the line direction, the magnet 61 or 65 preselectedby the reversing switch 62 is actuated which, via the correction membersdescribed with the aid of FIG. 6, brings the cranked lever 48 or 49 intoengagement in the limiting bore 29 until it stops on the adjusting screw67.

Clamped between cranked lever 48 or 49, precontrol roller 13 andlimiting bore 29, the tracer pin 5 is precontrolled in a predetermineddirection from which this same advance direction results. If this doesnot agree to the shape determined by the pattern, the side deflectionreduces or enlarges. This results in a rotation of the precontrol whichthe tracer multiplies against the pattern or controls away from thepattern until balance is found by the correct position.

By changing the line advance direction, an angular momentum of about 90is on the one hand given to the precontrol in the direction of the newtheoretical position, or on he other hand, the precontrol is switched bythe reversing switch 62 onto the other magnet 61, or 65, so that theother cranked lever shifted through 90 takes over the role of thepreviously active cranked lever.

A fourth embodiment is illustrated in FIGS. 23 to 25. As FIG. 23 shows,the construction of this embodiment is very similar to that of FIG. 1with the exception of the correcting element. No correction crankedlevers are provided to act against the roller 13 of the precontrol unit.

The data converter 9 is coupled via the amplfier-rectifier group 7 to aproportional solenoid 81 in such a manner that the action is independentof travel, which solenoid acts mechanically on the stationary" part ofthe data converter 22 (in this case on the coil) of the precontrol unit,which to this end is movable, and, biassed by a spring 80, is mounted onthe precontrol member. This data converter 22 controls the servomotor 16of the precontrol unit, as before, via the amplifier 17.

The correction effect is brought about in this case by changing thereference position of the stationary" part of the data converter 22 inthe precontrol member, this change of the reference position beingefi'ected proportionally to the value of the side deflection of thefeeler or tracer.

If the pin 5 is deflected by a sidewall 34 to the side when the line isstarted (FIG. 24), the magnet 81, due to the signal from the dataconverter 9, presses the coil of the data converter 22 inwardly againstthe spring 80. The position of rest of zero position of the precontrolis thereby changed. The precontrol subsequently attempts to reassumethis position of rest by beginning to rotate in a clockwise direction(FIGS. 24, 25).

The downwardly rotating precontrol roller 13 thus pushes the feeler ortracer pin upwards. This movement lasts until the new advance directionnecessary for tracing the side wall is assumed (FIG. 25). Each furtherpattern shape change increases or decreases the side deflection whicheffects a change of the precontrol rest position in a clockwise oranticlockwise direction, so that the tracer is raised from the patternor sunk into the pattern according to the lateral deflection.

Finally, in FIGS. 26 to 28, a fifth embodiment is shown, wherein thebasic construction is with the exception of the correcting members, verysimilar to that of the embodiment according to FIG. I or according toFIG. 23.

Again no correction cranked levers are provided. In their place, thecorrecting members are represented by a pair of proportional solenoidsand 87 which are directly coupled to the tracer pin 5 via spring rods 86or 88 (FIG. 27). These two solenoids work away from the pattern andtheir lifting direction forms an angle of about 60 to the longitudinalaxis of the pin 5.

The actuation of the solenoids 85 or 87 is effected due to the amplifiedsignal of the data transmitter 9. The reversal between solenoids 85 and87 is effected in dependence of the line advance direction by thereversing switch 92, but also additionally in dependence upon thevertical position of the pin 5 by actuation of a relay 91 by means of athreshold value switch based on the polarity of a further data converter89 which is coupled to the pin 5 via a cranked lever 93.

If the tracer is laterally deflected when the sidewall 34 is encountered(FIG. 27) the data converter 9 is brought from its neutral position. Itssignal proportional to the travel is amplified and fed to theproportional solenoid 87 which pulls the tracer with a travel,proportional to the lateral deflection, upwardly and obliquely againstthe force of the precontrol roller. In this way, the precontrol rotatesin a clockwise direction and assists the unwedging of the tracer fromthe pattern. These movements are effected until a balanced state isestablished in which the pin 5 is so precontrolled under the efiect ofsolenoid 87, precontrol roller 13 and pattern 34 that the advancedirection follows with the pressure necessary for tracing the pattern.If the sidewall retreats so that a descending direction results, thesolenoid 85 must prevent the tracer from wedging due to the rolleraction, instead of solenoid 87, by operating against this force. Thisrequires a reversal at the moment of passage through zero of thevertical movement which is undertaken by the data transmitter 89 bymeans of threshold value switch 90 and relay 91.

Also in this phase, each increased lateral deflection produces anamplifcation of the magnetic pulling force which draws the tracer fromthe wedged state. Any reduction of the side deflection reduces themagnetic force so that the tracer and consequently the advance directionis controlled by the increased effect of the precontrol roller againstthe pattern.

While in all the above described embodiments purely electrical,electromechanical and electronic switching elements are used, for thesake of simplicity, it should be understood that it remains within thejudgement of the man skilled in the art to replace one part or all theseswitching elements by corresponding hydraulic or mechanical controlelements, according to the actual circumstances, in order, for example,to redesign or complete an existing feeler or tracer as described inFIG. 8 of U.S. Pat. specification No. 3,114,295 to form a device asdescribed here.

I claim:

1. An automatic tracer assembly for a copying machine tool having apattern, a tracer member adapted to coact with said pattern, meansmounting said tracer member for pivotal movement and for axial movement,an automatic precontrol means exerting on said tracer member aprecontrol force in a direction at a constant angle to the direction ofa tangent at the point of contact between said tracer member and patternin a copying line plane, wherein the improvement comprises detectingmeans responsive to lateral deflections of said tracer member outside ofthe copying line plane to produce a signal in accordance to said lateraldeflections, amplifying means connected to said detecting means foramplifying said signal, and correcting means connected to saidamplifying means and responsive to the signal supplied therefrom to movesaid tracer member as if the lateral deflection were in the copying lineplane.

2. A tracer assembly as claimed in claim 11, wherein means resilientlybias said tracer member to a position centered in the line copying planeand said detecting means includes a data transmitter issuing a signalcharacterizing the amount of the tracer member deflections outside theline copying plane, said correcting means being actuated according tothis signal as amplified by said amplifying means.

3. A tracer assembly as claimed in claim 1, wherein said correctingmeans acts directly on the said tracer member.

4. A tracer assembly as claimed in claim 1, wherein said precontrolmeans for controlled by a proportionally operating reversing switch,said precontrol means in turn being actuated in dependence of the tracermember deflection in the line copying plane, wherein the correctingmeans is coupled to said reversing switch, in order to alter its neutralposition according to the tracer member deflection effected outside theline copying plane.

5. A tracer assembly as claimed in claim 3, wherein said correctingmeans comprises a pair of correcting members arranged symmetrically withrespect to the direction of operation of said precontrol means, saidcorrecting members being selectively operable depending upon thedirection of travel along the copying line plane, said correctingmembers operating in directions forming an obtuse angle with theoperating direction of the precontrol means.

6. A tracer assembly as claimed in claim 5, wherein said each correctingmeans includes at least one crank lever having one end operablyconnected to said detecting means and another end operably connected tosaid tracer member.

7. A tracer assembly as claimed in claim 2, wherein said datetransmitter is an electromechanical converter and said correcting meansincludes proportional solenoids and a reversing switch, the lattermovable to one position to connect said converter and one of saidproportional solenoids, and to another position for a short time toconnect both proportional solenoids to one another.

8. A tracer assembly as claimed in claim 4, wherein a relay which isautomatically reversible according to the direction of copying andoperates said reversing switch with change in direction of copying.

9. A tracer assembly as claimed in claim ll, wherein a threshold valueswitch is provided between the said detecting means and said correctingmeans and a comparison switch is connected in series with saidprecontrol means, said comparison switch receiving inputs from on theone hand a data transmitter giving the momentary position of theprecontrol means and on the other hand from said detecting means.

i l l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Jany 4 IInventor(s) Otto Ronner It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In column 1, line 14 change "as" to -a--; and in line 49 delete first"of". In column 2, line 70, change "inde pendent" to dependent--; and inline 74, change "pivotably" to pivotable. In column 3, line 14, change"date" to data. In column 4, line ll, change "activating" toactuating--; in line 12, change "connecting" to correcting-; and in line73, change first "by" to be. In column 5, line 45, change "he" to the-;and in line 72, change second "of" to or. In column 6, line 35, insertafter precontrol roller 13 is pressed outwardly, the preControl-; and inline 41, insert after descending advance. In column 7, Claim 2, change"ll" to l--. In column 8, Claim 6 before the word correcting delete"each"; in Claim 7, change "date" to data; and in Claim 9, change "ll"to l-.

Signed and sealed this 18th day oi July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,,JR. ROBERT GOTISCHALK Attesting Officer 4Commissioner of Patents 1050 10-69 ORM Po USCOMM-DC 6O376-P69 u.s.covzmmsm Pmmmc omce; use; woes-334

1. An automatic tracer assembly for a copying machine tool having apattern, a tracer member adapted to coact with said pattern, meansmounting said tracer member for pivotal movement and for axial movement,an automatic precontrol means exerting on said tracer member aprecontrol force in a direction at a constant angle to the direction ofa tangent at the point of contact between said tracer member and patternin a copying line plane, wherein the improvement comprises detectingmeans responsive to lateral deflections of said tracer member outside ofthe copying line plane to produce a signal in accordance to said lateraldeflections, amplifying means connected to said detecting means foramplifying said signal, and correcting means connected to saidamplifying means and responsive to the signal supplied therefrom to movesaid tracer member as if the lateral deflection were in the copying lineplane.
 2. A tracer assembly as claimed in claim 1, wherein meansresiliently bias said tracer member to a position centered in the linecopying plane and said detecting means includes a data transmitterissuing a signal characterizing the amount of the tracer memberdeflections outside the line copying plane, said correcting means beingactuated according to this signal as amplified by said amplifying means.3. A tracer assembly as claimed in claim 1, wherein said correctingmeans acts directly on the said tracer member.
 4. A tracer assembly asclaimed in claim 1, wherein said precontrol means for controlled by aproportionally operating reversing switch, said precontrol means in turnbeing actuated in dependence of the tracer member deflectIon in the linecopying plane, wherein the correcting means is coupled to said reversingswitch, in order to alter its neutral position according to the tracermember deflection effected outside the line copying plane.
 5. A tracerassembly as claimed in claim 3, wherein said correcting means comprisesa pair of correcting members arranged symmetrically with respect to thedirection of operation of said precontrol means, said correcting membersbeing selectively operable depending upon the direction of travel alongthe copying line plane, said correcting members operating in directionsforming an obtuse angle with the operating direction of the precontrolmeans.
 6. A tracer assembly as claimed in claim 5, wherein said eachcorrecting means includes at least one crank lever having one endoperably connected to said detecting means and another end operablyconnected to said tracer member.
 7. A tracer assembly as claimed inclaim 2, wherein said data transmitter is an electromechanical converterand said correcting means includes proportional solenoids and areversing switch, the latter movable to one position to connect saidconverter and one of said proportional solenoids, and to anotherposition for a short time to connect both proportional solenoids to oneanother.
 8. A tracer assembly as claimed in claim 4, wherein a relaywhich is automatically reversible according to the direction of copyingand operates said reversing switch with change in direction of copying.9. A tracer assembly as claimed in claim 1, wherein a threshold valueswitch is provided between the said detecting means and said correctingmeans and a comparison switch is connected in series with saidprecontrol means, said comparison switch receiving inputs from on theone hand a data transmitter giving the momentary position of theprecontrol means and on the other hand from said detecting means.